Abstract

Rheumatoid arthritis (RA) is a systemic inflammatory disease with polyarticular synovitis leading to formation of rheumatoid pannus and subsequent erosion of articular cartilage and bone. Prostaglandins (PGs)--a group of arachidonic acid metabolites found at elevated levels in synovial fluid and synovial membrane are considered to play a pivotal role in development of vasodilatation, fluid extravasation and pain in synovial tissues. Moreover, there is increasing evidence that PGs (especially prostaglandin E2) are mediators involved in complex interactions leading to development of erosions of articular cartilage and juxta-articular bone. Cyclooxygenase is an enzyme playing crucial role in PGs production. It is known that two forms of cyclooxygenase exist: cyclooxygenase-1 (COX-1) playing house-keeping functions and cyclooxygenase-2 (COX-2) involved in inflammatory responses. Synovial tissues from patients with RA are shown to contain COX-2 and to a less extent COX-1. COX-2 expression in rheumatoid synovium is induced by proinflammatory cytokines, mainly IL-1, while corticosteroids are capable of inhibiting COX-2 expression. The understanding of crucial role of COX-2 in synovial inflammation led to development of new group of anti-inflammatory agents--selective COX-2 inhibitors, that inhibit specifically COX-2, providing effective anti-inflammatory action without the side effects associated with inhibition of COX-1. In the context of widespread use of selective COX-2 inhibitors hypothetical role of COX-1 in RA pathology should be elucidated.